Development Of High-precision Direct Solar Spectral Irradiance Monitor

The sun is the dominant energy source for the earth.The changes of the solar radiation deeply affect the earth's climate and environment.The effects of solar radiation on terrestrial,oceanic and atmospheric systems are different.Ground-based observation of the direct solar spectral irradiance can provide data support for climatic research,automated vicarious calibration,and spectral irradiance traceability.At present,the measurement uncertainty of the ground-based solar spectral irradiance monitor is about 3%.It is difficult to adapt to the above application requirements that the demand uncertainty is 0.7%.In this paper,the development of solar spectral irradiance monitor is investigated at home and abroad.A design scheme of a solar direct spectral irradiance monitor that is used on the ground is presented.This article focuses on the opto-mechanical design of the irradiance monitor,and also introduces the design of the electronics and software of the irradiance monitor.The compact main light path with Fery prism as the dispersion and convergence element is designed to obtain solar spectral irradiance ranging from 380 nm to 2500 nm.The calibration light path with laser,slit,concave mirror and linear CCD as the main optical elements is designed,which is used for spectral calibration.A precise solar tracking light path with a four-quadrant detector as the main optical element is designed to tracke the sun accurately.The influence of temperature for the irradiance monitor is analyzed,and a temperature control device with a temperature deviation of better than 0.2? is designed for the Fery prism and the detector.The influence of stray light in the field of view of the irradiance monitor is simulated by LightTools.According to the result that the stray light energy accounts for about 0.1%of the total energy,it is verified that the irradiance monitor has a good suppression effect on stray light.The sealing and anti-fogging structure of the irradiance monitor is studied,which improves the reliability of the outdoor operation for the irradiance monitor.This paper studies the spectral calibration method based on the prism dispersion equation.A spectral calibration apparatus with a laser as the light source is set up to realize the wide spectrum calibration of the irradiance monitor,and the deviation is less than 0.3 nm.It is proven that the method of the spectral calibration is effective.The radiometric calibration apparatus with a standard lamp is established to obtain the spectral irradiance responsivity of the irradiance monitor.The uncertainty of the spectral irradiance responsivity is better than 0.69%.In order to improve the accuracy of radiometric calibration,the standard detector method used to obtain the spectral irradiance responsivity is studied.The calibration apparatus with the tunable laser,the integrating sphere,the standard detector is built.The standard detector is traceable to the cryogenic radiometer.The spectral irradiance response function is obtained by the standard detector method,and the uncertainty of the results is better than 0.46%.A simple iterative method is studied to recover the solar spectral irradiance that is super-resolution.The results obtained by the simple iterative method are compared with the calibrated value of the standard lamp.The deviation at the wavelength of 750.2 nm,799.3 nm,820.2 nm is less than 0.69%,which verifies the feasibility of the method.The measurement uncertainty of the irradiance monitor developed in this article is about 0.7%,and the direct solar spectral irradiance can be obtained accurately by this irradiance monitor on the ground.The irradiance monitor has broad application for climatic retrieval and automated vicarious calibration.